The present invention relates to electronic circuit oscillators and, more particularly, to electronic circuit oscillators which oscillate at millimeter wavelengths.
Oscillator circuits generate periodic electrical signals by converting a fraction of the constant polarity power supply thereto into a periodic signal output without requiring a period signal input. As such, oscillators at higher frequencies are millimeter wave and microwave energy sources for many kinds of high operating frequency systems. That is, oscillators at high frequencies are often precisely controlled frequency sources used in frequency conversions and in generating carriers for modulated signals in communication systems.
The advancements made in high frequency circuits and systems have increased the need for better performing oscillators. Some of the problems which arise from the use of high frequency oscillators are output signal amplitude stability and phase noise, i.e. variations in the oscillation frequency from the desired frequency, relatively large and costly oscillation systems because of the need for forming hybrid circuits requiring plural components mounted over an area in the device housing that requires interconnections, sometimes by hand, between those components, changing performance with changing temperatures, and reliability during use in many kinds of environments.
In addition, in many applications, the oscillator must be tunable with respect to the frequency of its output signal so that frequency can be varied by the user as desired. Additional problems which have been encountered in tunable oscillators are relatively narrow tuning frequency bandwidths, non-linear changes in the tuning frequency with the control variable, and long settling times for the output signal frequency and amplitude following a change made thereto by the tuning control variable. Thus, there is a desire for improved high frequency oscillators to reduce such problems, and particularly for high frequency tunable oscillators to reduce the added problems presented thereby.